Hi all - first post here on gitlab forums. Hoping I can provide more than enough info and do it in the proper(ish) format 
Problem:
When we attempt to manage access on a subgroup we are recieving a 500 error. Here is the error
Started GET "/groups/main_group/sub_group/-/group_members" for xx.xx.xxx.xxx at 2020-08-18 12:50:13 -0500
Processing by Groups::GroupMembersController#index as HTML
Parameters: {"group_id"=>"main_group/sub_group"}
Completed 500 Internal Server Error in 326ms (ActiveRecord: 75.3ms | Elasticsearch: 0.0ms | Allocations: 139585)
ActionView::Template::Error (undefined method `name' for nil:NilClass):
119: data: { confirm: leave_confirmation_message(member.source) },
120: class: "btn btn-remove align-self-center m-0 #{'ml-sm-2' unless force_mobile_view}"
121: - else
122: = link_to member,
123: method: :delete,
124: data: { confirm: remove_member_message(member), qa_selector: 'delete_member_button' },
125: class: "btn btn-remove align-self-center m-0 #{'ml-sm-2' unless force_mobile_view}",
app/helpers/members_helper.rb:18:in `remove_member_message'
Expectation:
I should be able to pull up and manage the all members and their access of sub_group with no errors.
What I expect the problem to be is that we had a situation where it appears that accounts were created with the username’s being a persons email address. so the name is not being properly pulled and thus causing an issue.
My other thought is that these users are no longer with the company but the invite has no expired and is somehow causing problems.
Here is my Gitlab version information:
GitLab12.10.0-ee (58d798bed62)
GitLab Shell12.2.0
GitLab Workhorsev8.30.1
GitLab APIv4
Ruby2.6.5p114
Rails6.0.2
PostgreSQL10.7